Silencer ring for pot-type burners



R.-N. ST. JOHN SILENCER RING FOR POT-TYPE BURNERS 2 Sheets-'-Shee t 1 June 15, 1954 Filed June 27, 1951 2, BY ATTORNEYS.

June 15,1954 R. N. ST. JOHN 256813- SILENCER RING FOR POT-TYPE BURNERS Fiied June 27, 1951 2 sheets-sheet 2 PRIOR ART ATTORNEYS.

Patented June 15, 1954 UNITED STATES PATENT OFFICE SILENCER RING FOR POT-TYPE BURNERS Application June 27, 1951, Serial No. 233,822

Claims. 1

My invention relates to a silencer ring for pottype burners, and more particularly for pot-type burners in which liquid. fuel is vaporized in the bottom of the pot and burned at a higher .level therein after the formation of a combustible mixture with the air entering through the air inlet ports.

Pot-type burners are presently in widespread use for the burning of oil and other liquid fuels. The development and refinement in the operation of these burners has been largely empirical, since very little theoretical knowledge has been developed concerning the laws governing the operation of these burners. However, by a gradual cutand-try process a very efficient burner has been developed. This burner is of comparatively simple construction. In its preferred form it consists of a cylindrical casing or pot closed at the bottom and open at the top. An oil inlet is provided to flow the oil onto the bottom surface from which it is vaporized so as to rise upwardly within the pot and out the open upper end. A feature of great importance in the structure is the provision of a particular arrangement of air inlet ports in the side walls of the pot for the admission of air to mix with the vaporized oil. While the number and size of these air inlet ports is subject to considerable variation, the arrangements are generally characterized by having a plurality of vertical spaced horizontal rows of primary air inlet ports and at least one row of secondary air ports above the primary air ports. It has been found desirable to have the lower row of primary air inlet ports downwardly orien tated to cause the air streams to sweep out the bottom of the pot, and to provide immediately thereabove an upwardly inclined baffle plate having a relatively large central opening through which the vaporized gases pass. There is also generally provided a flat burner top ring extending horizontally from the pot walls above the secondary air ports.

For maximum operating efficiency of the pot type burners described above, and especially in cold weather, it is often desired to maintain combustion therein at or near the optimum maximum capacity of the burner, during substantially all of the heating cycle. Thus, the normal high fire operation of these burners has become wellknown in the art. In that portion of the burner below the level of the secondary air ports there is maintained during high fire operation a fuel-air mixture which is so fuel-rich that ignition does not occur therein. At the secondary air port level, however, enough air is supplied and enough mixing occurs so that an envelope of flame originates at or near the secondary air ports and extends entirely around the pot. When the fuel-air ratio is maintained in correct adjustment, this flame envelope forms and holds as a tall, steady, and generally cylindrical wall of flames inside of which unburned gases rise and diffuse outwardly into the flame walls in much the same manner that a candle flame burns.

A rather serious problem of long standing arising in connection with the high fire operation of these burners is their tendency to make a rumbling noise when the ratio of fuel to air within the burner gets out of proper adjustment. In other words, at high fire these burners have a tendency toward fluctuating and unstable combustion when the normal fuel-air ratio is changed excessively. At present, the complicated fuel-aircontrols to prevent wide deviations from the ideal combustion ratios are not available to the industry. Therefore, this problem of burner rumble has long been a vexing one to the manufacturers and users of pot-type burners.

It is my belief that the reason why many suggested solutions for burner rumble have proved ineffective in preventing the rumble, or have so reduced the high fire capacity of the burner as to render them undesirable is because there was no complete theoretical understanding of the causes of burner rumble. My investigations of this problem have disclosed that burner rumble occurs under two sharply different sets of high fire conditions. One of these types, which has received some recognition, is the fuel-rich flame type of rumble which occurs when the burner is operated at draft values near or above normal and. a considerable excess of fuel is permitted to accumulate in the pot bottom. There is thus an extremely fuel-rich mixture of the fuel vapor and air which rises in the pot to the level of the secondary air ports. Because such a fuel-rich mixture burns more slowly than a normal or proper fuel-air mixture the flame can no longer hold at or near the secondary air ports but lifts or is blown away from these ports. When this condition becomes extreme, the lifting of the flame continues until the lower flame front or an appreciable portion of it rises above the inner edge of the top ring of the burner. I have discovered that this lifting of the secondary flame above the burner top ring over approximately 1 to 3 inches of its circumference permits the dipping of colder air and combustion products into the burner from above. This is instantly followed by a dipping of the main flame deep into the pot and then by the rapid alternate lifting and clipping of the flame front throughout a distance of perhaps twothirds of the pots depth. This rapid pulsating or rising and falling of the flame acts more or less like a diaphragm in a radio loud speaker and sets in motion air waves which create an objectionable rumbling noise, the volume and duration of which are determined by the exact operating conditions. Further, during this unstable flame period the flame is definitely carbonic in character and is very smoky,

Some investigators have suggested that this lifting of the flame is due to excessive air velocity through the secondary air ports; and that therefore some type of flame holding surface, placed near the ports would permit partial impingement of the jets thereon with a resulting reduction in velocity and better flame holding action. However, my analysis of this phase of the problem has led me to believe that the basic cause of the lifting of the flame is an excessively fuel-rich mixture which cannot be corrected by a simple flame holding surface. In other words, it is my conclusion that it is also necessary to correct the fuelair mixture ratio at the level of the secondary air ports.

A second type of condition, which I believe has largely been unrecognized, that produces burner rumble occurs when the burners are operated at or near normal high fire oil input rates in corn junction with very high draft values. With either a steady or pulsating high draft and a nor mal high fire oil rate, the effect of the high draft is to increase the percentage of air in the fuelair mixture as it rises within the burner. This leaner mixture burns more rapidly than the normal mixtures with the result that the main burner flame drops lower into the pot. Under extreme conditions, when the draft valuations approach three to six times those which are normal for high the operation, practically all of the burner flame is inside of the pot where it holds as a very turbulent, bright, active flame of considerable depth. In fact, it often extends from the top of the pot to a level from three to four inches lower, including the zones occupied by the secondary air ports and the two upper rows of primary air ports. I have discovered that this zone of turbulent flame is made up of horizontal sheets of flame which in turn are composed of horizontal circular flames, each surrounding an individual air jet as it enters the burner through the air ports of the burner side wall. Any slight vari ation in burner draft tends to deflect these horizontal jets and horizontal sheets of flame in a vertical direction. These sheets of flame then act as horizontal diaphragms in a vertical cylinder. That is, they respond to pressure changes and set up sound waves which in turn, as air waves, intensify the flame movement until under extreme conditions and objectionable burner rumble is produced. The loudest of these sound waves seems to be associated with the dancing of the flame between the secondary and upper primary air port levels.

It is therefore an object of my invention to provide means for substantially overcoming the problem of burner rumble of both the fuel-rich and fuel-lean types. Furthermore, it is an object of my invention to provide means for overcoming the problem of burner rumble, which will not interfere with the free mixing of fuel vapor with air in the burner, restrict the upward movement of the combustible gases, nor alter the character of the flame envelope at high fire in order that the high fire fuel burning capacity of the burner and its resulting heat output rating may not be reduced below present established levels. Morespeciflcally, it is an object of my invention to provide a silencer ring to be positioned beneath the burner top ring adjacent the secondary air ports, which will function to effectively stabilize the lower flame front of the burner flame at high fire near the levels of the top ring and the silencer ring during both fuel-lean and fuel-rich conditions, as well as during normal high fire operations. Further objects and advantages will appear as the specification proceeds.

My invention is illustrated in a preferred embodiment in the accompanying drawing, in which- Figure l is a partial plan view of the burner pct having the silencer ring of my invention incorpcrated therein, showing the top ring partially broken away .0 disclose the silencer ring therebelow; Fig. 2, a side sectional view taken in elevation of the pot-type burner of Fig. 1; Fig. 3, a perspective view of the silencer ring shown in position in Figs. 1 and 2; and Fig. 4., a partial sectional view of the upper portion of the burner shown in Fig. 2 illustrating the high fire operation or" the burner.

For purposes of clarity of explanation, the prior art burners are illustrated in Figs. 5 and 6. In Fig. 5 a high fire fuel-rich condition is shown, while Fig. 6 shows a high fire fuel-lean condition. It will be understood from the preceding discussion that both of these conditions have been found to be productive of an objectionable burner rumble when they become extreme.

Looking first primarily at Figs. 1 to 2 of the illustration given, there is shown a typical vaporizing burner pot iii having an open upper end i l and a closed bottom end i2. Preferably, the side walls E3 of pot it are of cylindrical configuration.

Liquid fuel is flowed. onto the top surface of bottom i 2 through inlet pipe 14. In starting the burner it is desirable to provide means for heat- 111g bottom 52, such as a pilot light, to initiate the vaporization of the liquid fuel. Upon being vaporized the fuel gases rise upwardly within chamber [5 bounded by walls i3. Air is supplied to the rising fuel vapors through a plurality of vertically spaced rows of primary air inlet DOItS Hi. In the illustration given, there are provided four horizontal rows of primary air inlet ports a, b, c and d. Ii desired, the bottom row (i of primary ports Hi can be downwardly orientated so that the enterin streams of air will sweep out the bottom of chamber i5. Also, the ports 58 in rows a, b, and. 0 can be formed horizontally in walls i3. It will be understood that the numher and diameter of the primary inlet ports I5 is such as to produce the normal high fire operation described above, in which the lower flame front is above the upper row a of primary air inlet ports. Since the details of this construction are well-known in the art, it is not believed that it will be necessary to further describe them herein.

In the illustration given, and preferably, there is provided between the two lower rows 0 and d of primary air inlet ports an upwardly inclined baiile plate H. In the illustration given, bafile plate i? is supported on a plurality of pins 88 spaced circumferentially on walls l3. It will be understood, however, that bafile plate I? can be omitted entirely, or a different type of bafiie plate substituted therefor.

Above the upper row a of primary air ports 16 there is provided at least one row of secondary air ports I9. In the illustration given, there are provided two vertically spaced horizontal rows e a d ,f of secondary air inlet ports. Preferably, the secondary ports I9 in rows 6 and f are upwardly orientated. It is the function of the secondary air ports to provide the additional amount of air to the rising mixture of fuel gases and primary air to produce combustion at the level of the secondary air ports during normal high fire operation.

As indicated above, pot-type burners have been generally equipped with a top ring which is secured to the walls I3 by any suitable means above the top row e of secondary air ports I9 and extends inwardly therefrom. While a top ring of this type is satisfactory in my improved burner structure, I prefer to employ a modification in the shape of top ring 20. In the illustration given the main portion of 26a of top ring 20 is upwardly inclined and has its inner edge turned upwardly rather sharply to provide an arcuate lip portion 28b. The purpose of having top ring 20 upwardly inclined or of frusto-conical shape is to prevent any downward deflection of the combustion gases which would cause the dipping of the flame front at the secondary level into the pot. In actual practice, it has been found that an upward slope of about 12 for portion Zila is satisfactory, while lip portion 26?) can have a radius of about one-half inch.

I have discovered that the employment of a silencer I'lllg of a particular configuration and in a particular position will substantially overcome the tendency of pot-type burners to produce a rumble for both fuel-rich and fuel-lean conditions without substantially reducing the capacity of the burner. This result is accomplished in the illustration given by mounting an upwardly inclined silencer ring 2i below top ring 28 adjacent secondary air ports I9 to provide an annular passage 22 between top ring 20 and silencer ring 2! and between pot walls I3 and silencer ring 25. To achieve the desired results, it is important that the bottom portion of passage 22 be in communication at a plurality of circumferentially spaced points with the peripheral regions of chamber I5 beneath silencer ring 2i and that the upper portion of passage 22 communicate with the central regions of chamber l5 above the silencer ring. It is also important that silencer ring 2| extend downwardly in closely spaced relation to the pot walls I3 across the paths of the air streams entering through the secondary air port I9 in the lower row f of secondary air ports. Thus, these air streams are made to impinge on the closely spaced surface of the silencer ring. Also, the closely spaced relationship of the lower portion of ring 2!! to walls I3 allows only a minor proportion of the rising combustible gases to pass through annular passage 22 and to be mixed therein with the secondary air.

Silencer ring 2! can be supported within chamber I 5 by an suitable means. In the illustration given, there are provided a plurality of circumferentially spaced pins 23 extending inwardly from not walls I3 upon which the lower edge of silencer ring 2! rests. Since the lower edge of ring 2i is of smaller diameter than the diameter of chamber 55, ring 2! can be supported on pins '23 and centered within chamber I5 so that there is provided entirely therearound an annular inlet port 24, as seen more clearly in Fig. l.

Preferably, silencer ring 2I is kinked to provide an upper portion 2Ia lying beneath portion 2M of top plate 26, and a generally vertical lower portion 2 lb adjacent pot walls I3 and extending across the air streams entering through ports I9 in row 1. In actual operation, it has been found desirable to have portion 21a slope upwardly at an angle of about 25 with respect to the horizontal, while portion Zlb is inclined at 10 with respect to the vertical.

Whenever top plate 28 is upwardly inclined, as preferred we have found it advantageous to have the silencer ring 2| and more particularly its upper portion am inclined upwardly at a steeper angle so that plate portions 26a and 2 I a converge upwardly to provide between their inner edges a Venturi-type outlet 25, as seen more clearly in Fig. 2. It will be understood, however, that a Venturi-type outlet can also be provided when top ring 2@ is substantially horizontal. In actual operation, I have found it desirable to have the frusto-conical surfaces provided by ring portions 2m and 2Ib converge from a clearance of onehalf to one inch at their outer edges to around one-fourth inch at their inner edges. I have also found it particularly desirable to employ an arcuate lip 20b on top ring 20 in conjunction with the Venturi-type opening 25 therebeneath. The arcuate lip Zllb prevents any tendency of the combustion gases and secondary air from being defiected downwardly and minimizes the possibility of cold air dipping into the chamber I5.

I have discovered that the operation of pottype burners employing the silencer ring of my invention can be further improved by corrugating or waving at least the upper portion of silencer ring 2 I. In the illustration given, upper portion 2 la is provided with circumferentially spaced non-radial corrugations 250 which produce a. Wavy configuration of the inner edge of ring 2i. Preferably, the corrugations or flutes in the upper portion Zia of silencer ring ZI are turned from radial lines between 5 to 30. Excellent results have been obtained when the central axis of the corrugations 2 io depart from radial lines by about 15. The purpose of the corrugations will be described in detail later in the specification.

In order to prevent any spilling of the entering secondary air below the lower edge of ring 2 I, it has been found desirable to extend ring portion 2 lb well below the line of impingement of the air streams thereon.

Operation In the operation of the pot-type burner illustrated in the drawings, the liquid fuel, which is generally fuel oil, is introduced through pipe I4 onto bottom I2 so as to form a pool thereon. Bottom i2 is then heated by means (not shown) to vaporize the liquid fuel, which then rises upwardly within chamber I5 after air enters through the primary and secondary air ports to mix with the fuel vapors to form a. combustible mixture which is then ignited. At normal high fire operation, the ratio of fuel to air is such that below the level of the secondary air ports ignition does not occur because of the excess of-fuel in the mixture. The lower flame front, as illustrated in Fig. 4, is at the level of the secondary air ports, or more specifically at the level of the inner edge of silencer ring 2!.

A small proportion of the fuel-rich mixture within chamber I5 below silencer'ring 2I passes upwardly through annular orifice 24 into passage 22. Air entering through the lower row 1 of secondary air ports I9 impinges on surface Zlb with the result that the velocity of the air streams is reduced and the flames surrounding the secondary air jets are prevented from lifting even when high draft values are combined temporarily with fuel-rich mixtures. The downward extension of surface 2 lb below the line of impingement thereon of the air streams entering through ports I9 in row f prevents the clipping or spilling of the cool incoming secondary air below the lower edge of the ring. This is especially important since the impingement of the air jets on the upper corner of surface 2 lb tends to cause a part of the air to dip and escape below the ring.

The ignited fuel-lean mixture in the lower portion of passage 22 is then passed upwardly and further mixed with the air streams entering through ports 39 of row 6 which impinge on surface Baa. In the preferred structure illustrated, the upward slope of both ring portions 26:: and 2m permits the upward progress of the burner gases, and their ez'nergence through opening at increased velocity without any downward deflection of these gases which would cause the dipping of the lower flame front into chamber It.

When the upper portion 250. of silencer ring 2! is provided with non-radial corrugations Zlc the secondary air is directed into the rising column of fuel-rich gas around. the periphery thereof and at different levels. There is thus produced a rotational and penetration effect which serves to open up the burner flame and increases its outer surface area. In actual operation, it has been found that the employment of corrugations reduces smoking at high oil input rates even though the draft is temporarily below normal.

The most important efiect of the silencer ring, however, is to substantially overcome the tendency of the burner to produce a rumbling noise at either fuel-rich or fuel-lean conditions. As illustrated in Fig. 4 there is provided within passage 22 a light blue flame B produced by the airrich mixture therein which holds near the secondary air ports at high as well as normal draft conditions. At the upper outlet 25 of passage 22 blue flame B merges with the main luminous orange colored flame O which has its lower flame front extending around the burner at the level of the inner edge of the silencer ring. Thus, under fuel-rich conditions combustion is still maintained within passage 22, and the flame therein is effectively merged with the main flame by employing the Venturi-type opening 25 and the non-radial corrugations 2 I 0.

Similarly, at fuel-lean conditions, combustion is maintained within passage 22 and the flame therein is merged with the main flame so that the secondary flame front is prevented from dipping into chamber i5. In producing this result, silencer ring, and particularly its upper portion 2i a physically separates the upper primary air port region from the secondary air port region. Thus, portion Zia served directly as a damping surface to effectively reduce or limit the vertical movements of the sheets of flame immediately above and below it. In other words, it effectively prevents the clipping of the secondary flame by providing a positive barrier against such dipping except at the extreme center of the burner.

In actual operation, it has been found that the employment of my silencer ring to eliminate burner rumble, does not result in any substantial reduction in the high fire fuel-burning capacity of the burner. In fact, with the employment of the Venturi-type opening and the corrugations, it has been found in some cases that the measured heat output rating of the burners is actually above the present established levels for burners without the silencer ring or other interior baffle members.

While in the foregoing specification I have set forth specific details for the purpose of illustrating an embodiment of my invention, it will be readily apparent to those skilled in the art that many of these details can be varied widely without departing from the spirit of my invention.

I claim:

1. In a vaporizing burner pot having in the walls thereof a plurality of vertically spaced rows of primary air inlet ports and at least one row of secondary air ports spaced above the primary air ports, said burner pot being adapted during normal high fire operation to provide a flame envelope originating at the level of the secondary air ports and into which the combustible gases rise and move outwardly into the flame walls, the improvement comprising in combination a top ring secured to the walls of said burner pot above said secondary air ports and extending inwardly therefrom, an upwardly inclined silencer ring mounted below said top ring adjacent said secondary air ports to provide an annular passage between said top ring and silencer ring and between said pot walls and silencer ring, the bottom portion of said passage communicating with the peripheral regions of the interior of said pot beneath said silencer ring and the upper portion of said passage communicating with the central regions of said pot above said silencer ring, said silencer ring providing a skirt portion extending downwardly therefrom in closely spaced relation to said pot walls and aligned with a portion of the secondary air ports, whereby the air streams entering through said portion of the secondary air ports will impinge on said skirt portion and so that only a minor proportion of the rising combustible gases passes through said annular passage and is mixed therein with the secondary air.

2. The combination of claim 1 in which said silencer ring is kinked to provide an upper portion lying beneath said top plate and a lower generally vertical portion adjacent said pot walls and extending across said air streams.

3. The combination of claim 2 in which the upper portion of said silencer ring is provided with a plurality of non-radial corrugations so that the inner edge thereof is waved, whereby the secondary air is caused to enter into the rising column of gases at diiferent levels and a rotational effect is produced.

4. The combination of claim 2 in which both the top ring and the upper portion of the silencer ring are inclined upwardly, and in which the upper portion of the silencer ring is inclined upwardly at a steeper angle than the top ring so that said rings converge to provide a Venturitype outlet thcrebetween.

5. The combination of claim 4: in which said top ring is provided with an upwardly turned arcuate lip around the inner edge thereof to prevent any tendency of the gases to be deflected downwardly.

6. In a vaporizing burner pot having in the walls thereof a plurality of vertically spaced rows of primary air inlet ports and at least two rows of secondary air ports spaced above the primary air ports, the lower row of said secondary air ports being upwardly orientated, said burner pot being adapted during normal high fire operation to provide a generally cylindrical flame envelope originating at the level of the secondary air ports and into which the combustible gases rise and move outwardly into the flame walls, the improvement comprising in combination a top ring secured to the walls of said burner pot immediately above said secondary air ports and extending inwardly therefrom, and an upwardly inclined silencer ring mounted below said top ring adjacent said secondary air ports to provide an annular passage between said top ring and silencer ring and between said pot walls and silencer ring, the bottom portion of said passage communicating around the circumference of said pot with the peripheral regions of the interior of said pot beneath said silencer ring and the upper portion of said passage communicating with the central regions of said pot above said silencer ring, said silencer ring providing a skirt portion extending downwardly therefrom in closely spaced relation to said pot walls and aligned with a portion of the secondary air ports, whereby the air streams entering through said portion of the secondary air ports will impinge on said skirt portion and so that only a minor proportion of the rising combustible gases passes through said annular passage and is mixed therein with the secondary air.

'7. The combination of claim 6 in which said silencer ring is kinked to provide an upper portion lying beneath said top plate and a lower generally vertical portion adjacent said pot walls and extending across said air streams.

8. The combination of claim 7 in which the upper portion of said silencer ring is provided with a plurality of non-radial corrugations so that the inner edge thereof is waved, whereby the secondary air is caused to enter into the rising column of gases at different levels and a rotational efiect is produced.

9. The combination of claim '7 in which both the top ring and the upper portion of the silencer ring are inclined upwardly, and in which the upper portion of the silencer ring is inclined upwardly at a steeper angle than the top ring so that said rings converge to provide a Venturitype outlet therebetween.

10. The combination of claim 9 in which said top ring is provided with an upwardly turned arcuate lip around the inner edge thereof to prevent any tendency of the gases to be deflected downwardly.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,806,566 Sturgis May 19, 1931 2,241,470 Miller May 13, 1941 2,261,814 Suchland Nov. 4, 1941 2,275,149 Howard Mar. 3, 1942 2,518,689 Hoger Aug. 15, 1950 

